Israel's security agencies had relied to some extent on the same Palestinian polls and opinion makers that led the media astray. Foreign Ministry spokesman Mark Regev noted that Palestinians and the international community also were taken by surprise. "We were not more wrong than anyone else," he said.

After the enormity of the Hamas win -- 76 of 132 Parliament seats -- became apparent Thursday, Acting Prime Minister Ehud Olmert instructed normally talkative Cabinet ministers not to speak to the media without permission. After a three-hour emergency session of the Security Cabinet, he issued a brief statement that Israel would not negotiate with a Palestinian government that includes Hamas ministers.

On Friday, acting Foreign Minister Tzipi Livni appealed to the international community to isolate any future Hamas government but refused to say what Israel might do.

For now, it appears Israel will hold off on drastic measures, such as sealing border crossings with Gaza or cutting off the monthly flow of tax rebates to the cash-starved Palestinian Authority. The new Palestinian government might not be formed for two months, giving Israel time to come up with a new policy.

Avi Dichter, former chief of the Shin Bet security service and a top official in Olmert's Kadima Party, said Israel must not be rash and must wait to see if Hamas will abandon its violent ideology once it assumes power.

Dichter raised the possibility of a Hamas about-face. "I think it would be illogical, or I would even say insane, for them (Hamas) to continue along the extremist line they have been following until today," he told Israel Radio.

In the run-up to Wednesday's Parliament election, Israel's security services had listed five possible scenarios, from Hamas getting less than 30 percent to an outright Hamas victory. The most likely outcome, the intelligence analysts told the government, was a narrow Fatah victory, with Hamas coming in a strong second.

The assessment was based in part on pre-election surveys by Palestinian pollster Khalil Shekaki who -- along with a second polling company linked to the West Bank's Bir Zeit University -- had predicted a Fatah victory.

The Bir Zeit pollster, Nader Said, said Friday he was still "in shock" over having missed by such a wide margin, even though he polled 8,000 voters, an unusually large sample. The pollster said the new electoral system -- half the candidates were chosen in districts, the other half from party slates -- contributed to the confusion. "We don't have enough experience (in democracy) to capture such a thing. It was the first real election of this kind," he said.

Diskin said then that the race is too close to call, Steinitz said Friday. The Shin Bet chief cited the polls predicting a narrow Fatah victory but said Hamas was better organized and could close the gap. "Yuval Diskin said he wouldn't be surprised if Hamas won," Steinitz said.

But Israel's military intelligence, which also prepared forecasts, said a major Hamas win was an "extreme scenario" of low probability, according to Alex Fishman, military commentator for the Yediot Ahronot daily.